<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .preview_wrap {
            position: relative;
            width: 500px;
            height: 500px;
            border: 1px solid #ccc;
            margin: 100px;
        }

        .mask {
            display: none;
            position: absolute;
            top: 0;
            left: 0;
            width: 300px;
            height: 300px;
            background-color: #ffe793;
            opacity: .6;
            cursor: move;
            z-index: 1;
        }

        .big {
            display: none;
            position: absolute;
            top: 0;
            left: 510px;
            width: 550px;
            height: 550px;
            border: 1px solid #ccc;
            overflow: hidden;
        }

        .bigImg {
            width: 920px;
            position: absolute;
            top: 0;
            left: 0;
        }

        .xiao {
            width: 500px;
        }
    </style>
    <script src="10-1.js"></script>
</head>

<body>
    <div class="preview_wrap">
        <div class="preview_img">
            <img src="images/da.jfif" alt="" class="xiao">
        </div>
        <div class="mask"></div>
        <div class="big">
            <img src="images/da.jfif" alt="" class="bigImg">
        </div>
    </div>
</body>

</html>